The present invention relates to the field of optics and, more particularly, to an integrated optical apparatus providing more than one signal in separate return paths.
Many typical computer systems include a disk drive cooperating with storage media to permit storage and retrieval of data. A typical optical disk drive includes an optical head that conventionally uses a laser to transmit light to the optical disk. Light reflected from the surface of the disk is detected by an optical detector and processed to read data from the disk. An example of such an optical head is disclosed, for example, in U.S. Pat. No. 5,204,516 titled xe2x80x9cPlanar Optical Scanning Head Having Deficiency Correcting Gratingxe2x80x9d by Opheij.
The size of the various optical head components, however, are often too large for many desired applications and many market demands. Also, as densities of integrated circuits and system boards increase, the demand for smaller components increases. Additionally, the production process for a conventional optical head requires that the laser be excited or turned-on (i.e., xe2x80x9cactive alignmentxe2x80x9d) for 25 alignment of the laser, the detector, and the optical elements. An example of active alignment processes is illustrated and described in an article 10 published in Optical Engineering (June 1989) titled xe2x80x9cHolographic Optical Head For Compact Disk Applicationsxe2x80x9d by Lee.
Unfortunately, these active alignment requirements are complex, time consuming, and relatively expensive. Further, the level of size reduction in the vertical direction of an optical head is limited. In addition, the relatively large size of the elements of an optical head which can be manipulated is determined by the need for active alignment.
With the foregoing background in mind, it is therefore an object of the present invention to provide an optical head, such as for a disk drive, and related methods which is more compact and less expensive to manufacture. It is further an object of the present invention to provide more than one signal having unique return paths.
These and other objects, advantages, and features of the present invention are provided by an integrated optical head having more than one or no optical elements in a return path from a target, thereby forming unique return paths for each beam. The integrated optical head preferably includes an optically transparent substrate having first and second faces. The substrate may include a diffractive optical element formed on a face thereof. A light source, such as a laser, is positioned adjacent the first face of the substrate to transmit light through the substrate, through the diffractive optical element, and toward a target, such as optical storage media. An optical element provided in the substrate splits the light from the light source into more than one beam. An optical detector is positioned adjacent the first surface of the substrate to detect respective beams reflected from the target and through the substrate. All of the optical elements needed to create the more than one beam, direct the more than one beam onto the target, and direct the more than one beam form the target onto said detector are on the substrate and/or any structure bonded to the substrate. Preferably, the detector includes more than one detecting element for detecting respective beams of the more than one beam.
In another embodiment, a second transparent substrate is aligned and joined to the first substrate. The second substrate may carry one or more optical elements. According to this aspect of the invention, alignment areas in the form of benches or other mechanical features may be formed in one surface and mating recesses, for example, may be formed in the other surface. Adhesive attachment areas, which may overlap the alignment areas, hold the substrates together. Alignment may also be accomplished at the wafer level by having the elements of each die accurately placed using photolithography to accurately align the two wafers. The assembled dies can then be diced without the individual alignment means or steps being required for connecting the first and second substrates.
These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples are given by way of illustration only and are directed to the preferred embodiments of the present invention, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.